BFE学习小分队习题

week2.js

class NestedIterator {
  constructor(iteratee = []) {
    this.stack = [[iteratee, 0]];
  }

  getTop() {
    const topIndex = this.stack.length - 1;

    if (topIndex < 0) {
      return null;
    }

    return this.stack[topIndex];
  }

  setTop(v) {
    const topIndex = this.stack.length - 1;

    if (topIndex < 0) {
      return null;
    }

    this.stack[topIndex] = v;
  }

  hasNext() {
    const top = this.getTop();

    if (top === null) {
      return false;
    }

    const [iteratee, cursor] = top;

    return iteratee.length - 1 >= cursor;
  }

  next() {
    const [iteratee, cursor] = this.getTop();
    const next = iteratee[cursor];

    if (cursor === iteratee.length - 1) {
      this.stack.pop();
    } else {
      this.setTop([iteratee, cursor + 1]);
    }

    if (next instanceof Array) {
      if (next.length !== 0) {
        this.stack.push([next, 0]);
      }

      return this.next();
    }

    return next;
  }
}

const v = [[], 2, [1,[]], [3, [4, [5, [], [], [[[], []], []], [6, 7, 8, 9, [10, [11, 12], 13], 14], 15], 16], 17]];
const a = [];
const n = new NestedIterator(v);
while (n.hasNext()) {
  // console.log(n.next(), JSON.stringify(n.stack), n.hasNext());
  a.push(Number(n.next()))
}

console.log(JSON.stringify(a));